Microburst of wind. Microbursts are small, concentrated downbursts of wind that travels vertically downwards from the base of storms. They are produced when dry or wet air suddenly becomes colder due to the cooling effect of evaporation in a thunder or rain cloud. This causes the air column to move rapidly downwards. If the air was initially dry, the winds may only be seen because dust is raised at the edges. If the air was wet, the microburst is accompanied by rainfall. Microbursts can cause planes to crash. Microbursts affect areas less than 5 kilometres across, whereas similar winds affecting a larger area are called a macrobursts.